Turning graphene magnetic is a promising challenge to make it an active material for spintronics. Predictions state that graphene structures with specific shapes can spontaneously develop magnetism driven by Coulomb repulsion of π-electrons, but its experimental verification is demanding. Here, we report on the observation and manipulation of individual magnetic moments in graphene open-shell nanostructures on a gold surface. Using scanning tunneling spectroscopy, we detect the presence of single electron spins localized around certain zigzag sites of the carbon backbone via the Kondo effect. We find near-by spins coupled into a singlet ground state and quantify their exchange interaction via singlet-triplet inelastic electron excitations. Theoretical simulations picture how electron correlations result in spin-polarized radical states with the experimentally observed spatial distributions. Extra hydrogen atoms bound to radical sites quench their magnetic moment and switch the spin of the nanostructure in half-integer amounts. Our work demonstrates the intrinsic π-paramagnetism of graphene nanostructures.

中文翻译：

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石墨烯开壳纳米结构中的单自旋定位和操纵。

使石墨烯磁性材料成为自旋电子学的活性材料是一个有前途的挑战。预测表明，具有特定形状的石墨烯结构可以在π电子的库仑排斥作用下自发地发展磁性，但是需要进行实验验证。在这里，我们报告在金表面上的石墨烯开壳纳米结构中的单个磁矩的观察和操纵。使用扫描隧道光谱法，我们通过近藤效应检测到碳主链的某些锯齿形位点附近存在的单个电子自旋的存在。我们发现耦合到单重态基态的近旁自旋，并通过单重态-三重态非弹性电子激发来量化它们的交换相互作用。理论仿真描绘了电子相关性如何产生具有实验观察到的空间分布的自旋极化自由基态。结合到自由基位点的额外氢原子淬灭了它们的磁矩，并以半整数的量切换了纳米结构的自旋。我们的工作证明了石墨烯纳米结构的内在π顺磁性。